In general I would not be single homed to a tier 1 ISP. You are better off using an ISP that has N upstream transit providers. That way they have multiple choices to select the best route. If you accept a default route from multiple upstreams you will be multi homed for inbound traffic but effectively single homed for outbound. Your router will select one default route and send 100% of the traffic that way. Instead of letting the router select a random default route, you should evaluate and rank your upstreams. Use a route map to set priority on the routes. Nobody has the best routes for all destinations, so you will have to find the one with the best average or perhaps the one that avoids bad routes. And that brings me to the point about Cogent. We used to have two upstreams. One was a local tier 2 ISP and the other was Cogent. Our quality was OK but if the tier 2 ISP link was down our customers would immediately call to claim downtime. We would not actually be down but quality was so low that people thought we were. The reason is that some major destinations from the Cogent network is routed from Europe to USA and back again. Latency go from a few milliseconds to 100 times worse. Available bandwidth is very reduced. Video from major streaming services will not play or only in lowest quality setting. I will claim that it is impossible to be single homed on Cogent in Denmark as an eyeball network. It is probably different if you are in the USA. This does not mean Cogent are useless. We were happy with the quality of the network and the price is good. What we experienced was bad peering. You just can't have them as your only transit. Regards Baldur Den 2. mar. 2017 21.02 skrev "Chuck Anderson" <cra@wpi.edu>: Define "good" vs. "bad" transport of bits. As long as there is adequate bandwidth and low latency, who cares? On Thu, Mar 02, 2017 at 08:30:37PM +0100, Baldur Norddahl wrote:

That will have the effect of prioritizing Cogent routes as that would be more specific than the default routes from the other providers. Cogent are not that good that you would want to do that.

Den 2. mar. 2017 20.16 skrev "Jeff Waddell" <jeff+nanog@waddellsolutions. com

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Or at least ask for a full view from Cogent - then you won't get any routes they don't have

On Thu, Mar 2, 2017 at 1:58 PM, Alarig Le Lay <alarig@swordarmor.fr> wrote:

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On jeu. 2 mars 12:36:04 2017, Aaron Gould wrote:

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Well, I asked my (3) upstream providers to only send me a ipv6 default route and they sent me ::/0...here's one of them...

Why did you don’t ask for a full view? With that, you can easily deal with that kind of problem.